The only wounds that really need closure are ones that are large enough and so poorly located that they gape open or are pulled open during movement. If the wound margins close naturally and stay closed automatically then there is no need for anything other than a covering to keep dirt out.

Size isn't a very good guide of what to close or not. A not very deep or wide cut over a joint may need stitching or closure if it won't stay closed. On the other hand a rather wide cut in another location may stay stable and closed all on its own.

The good news is that human skin is remarkably self-sealing. Even huge lacerations that should have been stitched will usually heal in time. It will take more time, hurt more and it increases the risk of outside infection but given time they usually knit. Often leaving a hell of an ugly scar but man spent the first hundred thousand years without stitches and we, for the most part, made it.

And, of course, if you have a paper cut there is no need to stitch or close anything. Mama's kiss and a Power Ranger band-aid will do it.